Can we make injectable materials that are as tough as the tissues that they are intended to replace?

Hi all,

I’d like to utilise this platform to pose the question as titled, and hopefully stimulate some discussion around alternative methods for the following point…

My specific area of interest is around mechanical properties of injectable materials, as well as host response. These are ‘old questions’ if you like, but remain unanswered. Many of the injectable materials have mechanical properties far inferior to the biological tissues that they replace. The answer to this question, in my opinion, comes down to molecular weight and molecular interactions but many of the processes that turn low molecular weight polymers into high molecular weight (or crosslinked) polymers require highly toxic species (initiators, crosslinkers, etc) but is there a more biologically friendly way of doing this?

I very much look forward to hearing your thoughts.

Kind regards,


Hi Owen,
What’s about using complexation with metal? eg calcium induced alginate gelation. It’s a kind of reversible crosslink but I guess more friendly than acrylate. Cellink company uses this technique to strengthen the 3D object after printing



Hi Thomas,

Thanks for your reply. Glad that you choose that material to discuss as it is one I have considerable interest in. Sure, metal ions can certainly increase interactions between alginate chains, producing a degree of stiffness to the hydrogels. We can also use other ions like gallium, aluminium, barium; which seem to produce materials with better strengths. However, these physical/ionic crosslinks have limited strengths and toughness remains relatively low compared to covalently crosslinked hydrogels like pHEMA.

Particularly when we look at orthopaedic cements like PMMAs; even at these relatively high molecular weights the materials remain quite brittle compared to the biological materials that they replace.

Are there ways of producing these high molecular weight materials that do not include the problematic side-effects of cytotoxicity? Can we utilise ‘click chemistry’ or some other chemistry to produce strong, stable covalent bonds, without the side-effects?



Hi Owen,

It is pretty straightforward to crosslink covalently whatever functional groups you want, using biocompatible crosslinkers. There are many simple strategies no need to use click chemistry if you do not want.

PMMA is different though.


Hi Maurice,

Thanks for your input. Can you discuss some of these strategies in more detail?